
Hi @Brian Henry ,
Microsoft 365 is a subscription service that ensures you always have the most up-to-date modern productivity tools from Microsoft.
Both products give you access to the same apps with the latest core features, some significant differences come down to the cost of ownership and the list of enhancements.
You can have a look for the difference between Microsoft 365 and Office 2019 over here:
What's the difference between Microsoft 365 and Office 2019?
https://support.microsoft.com/en-us/office/what-s-the-difference-between-microsoft-365-and-office-2019-ed447ebf-6060-46f9-9e90-a239bd27eb96
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Best regards,
Leon